Skin inflammation involves local production of cytokines, which mediate recruitment of leucocytes and altered gene expression and cellular phenotypes of keratinocytes and other cells residing in the skin. lnterleukin-1 (IL-1) is an important mediator of local and systemic inflammation. IL-1 acts via a receptor complex involving the IL-1 receptor type I (IL-1RI) and membrane bound IL-1 receptor accessory protein (mlL-1 RAcP). A soluble isoform of IL-1 RAcP (slL-1 RAcP) appears to be an inhibitor of IL-1 signaling. The Principal Investigator has identified a novel soluble isoform of IL-1 RAcP, slL-1RAcP-(3, which has a unique C-terminus. Recently discovered cytokines, related to IL-1, appear to have activities similar to IL-1, but act via a different membrane receptor, IL-1 receptor related protein 2 (IL-1Rrp2). IL-1Rrp2 is primarily expressed in epithelial tissues, and preliminary data suggests that different IL-1 family members orchestrate distinct immune responses by inducing distinct cytokine expression profiles in primary human keratinocytes. Interestingly, IL-1 Rrp2 also utilizes mlL-1 RAcP for intracellular signaling. The primary hypothesis is that the two different isoforms of soluble IL-1 RAcP, slL-1 RAcP and slL-1 RAcP-|3, may inhibit the activities of all IL-1 family members or a sub-set of these. Furthermore, proportional expression of the three different isoforms of IL-1 RAcP may determine cellular responses to inflammatory stimuli. Since IL-1Rrp2 is primarily expressed in epithelial cells the involved mechanism may play a significant role in skin homeostasis and inflammation. ecombinant soluble IL-1 RAcP proteins will be expressed and purified. Human keratinocytes will be treated with agonist IL-1 family members and activation of gene expression will be examined using quantitative reverse transcription PCR and ELISA assays. Activities of the two soluble IL-1 RAcP isoforms will be examined in co-treatment experiments with individual cytokines. Expression of the three different IL-1 RacP isoforms and the IL-1 family members in keratinocytes will be determined following treatments with known modulators of IL-1 RAcP proportional expression and members of the IL-1 family. This project will provide novel information about the function(s) of the novel IL-1 related cytokines and the two soluble IL-1 RacP isoforms. The ultimate goals are to elucidate molecular mechanisms regulating inflammation, identify defective pathways in diseases and utilize this knowledge to develop novel anti-inflammatory therapies. of this work would greatly benefit arthritic and musculoskeletal therapeutic areas.